1. Technical Field
The present invention relates to a method and an apparatus for determining an angle of each axis of a six-axis robot based on a result of teaching of a position and an attitude (position/attitude) of a hand of the six-axis robot through teaching.
2. Related Art
A six-axis robot includes first to sixth axes, and is capable of taking an attitude (posture) in which a rotation axis of the fourth axis and a rotation axis of the sixth axis robot match.
For example, in a perpendicular articulated six-axis robot, the rotation axes of a fourth axis and a sixth axis of the six-axis robot match when the six-axis robot takes an attitude (posture) in which a hand of the six-axis robot faces the vertical direction. In this attitude, the number of combinations of the respective angles of the fourth axis and the sixth axis is infinite. Therefore, the attitude is a singular point (singularity) at which a solution of the angle is not uniquely determined.
When the six-axis robot is taught by continuous pass (CP) teaching, the angle of each axis for each position/attitude is uniquely determined. Therefore, the singular point is not an issue. In addition, the singular point is also not an issue when point-to-point (PTP) teaching is performed, if the user specifies the angle of each axis for each position/attitude. The singular point becomes an issue in PTP teaching when only the position/attitude is specified and the angle of each axis is to be determined by inverse transformation.
Conventionally, the singular point is processed as an error. Therefore, a user is forced to avoid singular points. Alternatively, the user is forced to take measures, such as individually specifying the angles of not only the fourth axis and the sixth axis, but also the angles of the remaining axes. As a result, work load on the user also increases.